There are known in the prior art sound-attenuating earcup assemblies which are provided with earphones which afford communication with others by way of an intercom system or the like. In such assemblies the earphone is received in a recess in an isolating pad positioned within the hard outer shell adjacent to the open end thereof. The pad is formed of foam rubber and is provided with an opening leading from the earphone to the wearer's ear. A foam pad spaces the isolating pad from a cover assembled over a switch housing formed in the wall of the cup. A sound-attenuating earcup of the type just described is shown, for example, in Frieder, Jr. et al U.S. Pat. No. 4,023,209, issued May 17, 1977.
Assemblies of the type described above typically require earcups which enclose an appreciable volume of air. For example, helmets used by military combat vehicle crewmen require large-cavity earcups to provide adequate sound attenuation and ear protection. However, attempts to mount earphones in large-cavity earcups using an arrangement such as that shown in the Frieder et al patent have not proved satisfactory. With such an arrangement it has been found that the large-cavity earcup adversely affects the operation of the earphones. This is due to the fact that most earphones are designed to provide a satisfactory response in a 6 cc coupler and, therefore, when they are installed in a large volume earcup (over 100 cc) the response deteriorates at lower frequencies, severely affecting intelligibility in communication. In addition, systems of the prior art do not permit close coupling of the earphone to the ear without discomfort.